1. Field of the Invention
The present invention relates to an ink jet recording head that performs recording by discharging ink onto a recording medium such as paper or cloth, a printing apparatus employing this recording head, and a manufacturing method for this recording head.
2. Description of the Related Art
Hitherto, printing apparatuses such as printers, copiers, facsimiles or the like are configured to record images comprising dot patterns on a recording material based on image information. These printing apparatuses can be classified into an ink jet system, wire dot system, thermal system, laser beam system and so on, in accordance with a printing system. Of these systems, the ink jet system is configured to have an ink jet recording head and an energy converting unit for generating a discharge energy used for discharging ink on a liquid path thereof, and introduce ink from an ink supply port into the liquid path via a liquid chamber. Here, the ink jet system causes the ink drops to fly toward a recording material as flying liquid drops by using the discharge energy given to the ink by the energy converting unit, and performs recording by the shooting of the liquid-drops onto the recording material. Among others, the ink jet recording head, which discharges ink by making use of thermal energy, is in practical use, because the ink jet recording head has advantages in that it allows ink discharge ports for discharging ink drops for recording to form flying drops, to be arranged in a high density, and also enables the overall size thereof to be easily reduced. In recent years, with the demand for high speed recording, the number of nozzles arranged on the ink jet recording head has been increased.
In the ink jet system, because ink as a liquid is treated as an object, there may be cases where meniscus oscillations at discharge port portions are significantly disturbed by ink oscillations associated with continuous driving to thereby cause degradation of image quality. Particularly in the ink jet recording head having multi-nozzles arranged therein in a high density, the ink flow per unit time is high, and therefore, the forward inertia force acting on ink in a tank system becomes large when discharge is stopped, so that the nozzles are subjected to a positive pressure by the inertia force, and the meniscus of each ink drops becomes popped out. If the next print signal enters at this time, small ink drops splash and unfavorably results in a so-called splashing-fashioned print. FIG. 6 is a diagram of pressure oscillation waveforms in an ink flow path plotted against discharge pulses when a predetermined discharge was conducted in a conventional ink jet recording head. xe2x80x9cAxe2x80x9d, xe2x80x9cBxe2x80x9d, and xe2x80x9cCxe2x80x9d which are shown in FIG. 6 denote xe2x80x9ca period before a start of dischargexe2x80x9d, xe2x80x9ca discharging periodxe2x80x9d, and xe2x80x9ca period immediately after the stoppage of dischargexe2x80x9d, respectively. It can be seen from this diagram that the pressure oscillation amplitude (a) in the flow path after the stoppage of discharge comprises a large positive pressure value. These oscillations will disturb meniscus oscillations at the next discharge. Methods for eliminating such a phenomenon include a method by which meniscus oscillations are stabilized by adjusting flow resistance by the change in filter diameter or the changeover of ink flow path, and a method by which pressure oscillations are absorbed by forming a buffer chamber at a position midway through ink path to thereby allow bubbles to exist therein. The latter method using a buffer chamber is effective as a method for inhibiting pressure oscillations, and has been adopted for many types of ink jet recording heads.
Hitherto, a buffer chamber has been provided at a flow path portion connecting a head unit (element substrate) and a tank. However, because the buffer chamber has been far away from the head unit, it has not necessarily been able to respond to abrupt changes, although it has exerted an effect in refilling. Therefore, there has been request for a large-capacity buffer chamber provided near the head.
It is necessary for the buffer chamber to be configured so that a liquid is made difficult to enter thereinto by previously making the buffer chamber a closed space, in order to prevent gas in the buffer chamber from being replaced with ink. In this case, if dirt or the like has previously entered the buffer chamber, it is difficult to be removed by cleaning. Therefore, there has been possibility that the dirt or the like enters the flow paths during usage, and that the residual dirt or the like causes defective printing.
In addition, a drying operation after cleaning has unfavorably taken much time.
It is, therefore, an object of the present invention to provide an ink jet recording head having a buffer chamber with a large capacity near the element substrate and enabling the buffer chamber allowing gas to exist, to be sufficiently cleaned, and a method for manufacturing the same.
To solve the above-described object, the present invention provides an ink jet recording head that includes discharge ports each for discharging ink, flow paths each communicating with a respective one of the discharging ports; a common liquid chamber for supplying ink to the ink flow paths, an element substrate having discharge energy generating elements, and a holding member holding the element substrate and having the common liquid chamber and a plurality of paths communicating with the common liquid chamber. A portion of the plurality of paths is used as an ink supply path, and the other portion thereof is used as an air holding section formed by blocking an end portion of the path, opposed to the end portion thereof communicating with the common liquid chamber.
Also, to solve the above-described object, the present invention provide a method for manufacturing an ink jet recording head that includes discharge ports each for discharging ink, flow paths each communicating with a respective one of the discharging ports, a common liquid chamber for supplying ink to the ink flow paths, and an element substrate having discharge energy generating elements. This method comprises the step of providing the ink jet recording head with a holding member that holds the element substrate and that has the common liquid chamber and a plurality of paths communicating with the common liquid chamber, the step of joining the element substrate to the holding member, and the step of forming an air holding section by blocking an end of the path, opposite to the end thereof communicating with the common liquid chamber.
By virtue of the described features, the present invention makes it possible to provide a buffer chamber with a large capacity near the element substrate, sufficiently clean the buffer chamber allowing gas to exist, inhibit pressure oscillations in flow paths caused by ink oscillations during ink discharge to thereby maintain stable discharging conditions, and acquire a high-quality image at all times.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.